This invention relates in general to impact line printers that have a character chain printing mechanism that rotates on a hard support surface and more particularly to the lubrication of such a line printer character chain mechanism.
Impact line printers may print utilizing a rotating chain that has raised linguistic characters, such as alphanumerics, on the exposed exterior surface thereof. For example, in such a printer the character chain may be rotated at a high speed and hammers may be selectively actuated in a properly timed manner to impact selected areas of the paper (or another record medium) such that the paper impacts with a ribbon which then impacts upon the raised linguistic characters on the character chain of the line printer as the characters are in motion. A 1500 line per minute printer may have a character chain that moves at a velocity of 210 inches per second. The chain must move over a hard, smooth support surface such that the chain is firmly supported when impacted. The support surface must also be hard and smooth so that it will not significantly wear down over time and so that the chain will remain taut for proper operation. Commonly, both the character chain and the support surface are made of hardened steel.
Experience has shown that such line printer character chains must be lubricated for proper operation. However, if too little lubricant is provided between the line printer character chain and the hard support surface, the surfaces will heat up and seize together. On the other hand, if too much lubricant is provided between the line printer character chain and the hard support surface, the lubricant will get on the other parts of the line printer, the paper being printed by the line printer, and/or the characters on the chain to cause smudging of the printing.
A known printer character chain lubricating device has an oil reservoir from which oil is dropped at intervals (provided by an electronic timer) upon a felt wick. The oil passes down the wick, one end of which is located under a nylon wear surface which contacts the chains surface. Two little holes in the nylon surface permit the oil from the wick to be pumped onto the surface of the nylon in contact with the chain as the chain passes thereover. Such a system is rather expensive, does not necessarily dispense the proper amount of oil needed, and in general is not as reliable as is desired.
Thus, a line printer character chain lubricating device that provides a precise amount of lubricant on a need only basis would be very desirable. Such a device of course must also be inexpensive, reliable and require little maintenance and downtime.